Classifying muffler

ABSTRACT

Muffler for classifying and separating entrained oil and water from exhaust air of pneumatic devices. Exhaust air is led into a relatively unrestricted expansion chamber and passes into a silencing chamber through a collector against which droplets of entrained liquid and condensed vapors impinge. The relatively liquid-free air is diffused through the porous side of the silencing chamber. Impinged droplets collect to allow liquid to fall to base of silencing chamber in drops sufficiently large to prevent re-entrainment. Base of silencing chamber provided with means to permit draining, which may be automatic.

Unlted States Patent 91 1 ,811,251 Gibel May 21, 1974 [5 1 CLASSIFYINGMUFFLER 5.559.764 2/1971 Wheeler. Jr. 55/225 [76] Inventor: I Stephen J.l, 5 qgert 3,688,868 8/1971 Glbel 181/36 A I Rd., North Royalton, 0111044133 Primary Examiner Bemard Nozick [22] Filed: Aug. 25, 1971 Attorney,Agent, or Firm-Ely; Golrick & Flynn [21] Appl. No.: 174,860 ABSTRACTMuffler for classifying and separating entrained oil [52] Cl ig i andwater from exhaust air of pneumatic devices. Ex [51 1 Int Cl d 50/00haust air isled into a relatively unrestricted expansion [58] Fieid 6319 320 chamber and passes into a silencing chamber through e c 181/36 acollector against which droplets of entrained liquid and condensedvapors impinge. The relatively liquidfree air is diffused through theporous side of the si- [561 References Cited lencing chamber. lmpingeddroplets collect to allow .UNITED STATES PATENTS liquid to fall to baseof silencing chamber in drops suf- 2 .419.664 4/l947 ficiently large toprevent re-entrainment. Base of si- 2-514996 v7/195O lencing chamberprovided with means to permit drain- 25804555 [/1952 ing, which may beautomatic. 2.815.088 12/1957 10 Claims, 3 Drawing Figures 1 CLASSIFYINGMUFFLER on the one hand, diminish the hazards to health inherent in thefrequently unpleasant working conditions where such tools are employedand, on the other hand, prolong the life of such mufflers and increasethe efficiency of pneumatically operated devices. These results areobtained by classifying and separating, prior to final silenceddissemination of the exhaust air to the ambient atmosphere, variousvapors and droplets of liquid characteristically entrained in the airentering the muffler.

Pneumatic tools, such as drills, grinders, hammers, wrenches,screw-drivers, etc.; pneumatic equipment such as cylinders, brakes,clutches, etc.; and other pneumatic devices, such as valves, operated bycom- I pressed air nearly always require some sort of muffler orsilencer for quieting the shrill exhaust noise which would otherwise beintolerable. Such exhaust noise may otherwise vary from a relativelycontinuous scream, in the case of relatively constantly operated toolsand motors to sharp, startling reports, in the case of intermittentlyoperated clutches, brakes, cylinders, valves, etc. In theory suchexhaust air should be relatively free of contaminants such as dust andliquid particles; the air is usually filtered as it enters thecompressors and, after the air is compressed, efficient in-line filters,equipped with collecting bowls and automatic emptying valves,arenormally installed in the highpressure air line between thecompressors and the pneumatically operated means. In actual practice,however, the exhausted compressed. air contains moisture resulting fromvapor which remains in the air throughout its travel from the entranceof the compressor to its exhaust and boththe compressors and thepneumatically'opera'ted devices must be well lubricated. Thus, very finedroplets and vapors of lubricants become entrained with droplets ofmoisture in the exhaust air.

Unless removed by the exhaust silencing means, the presence of entrainedlubricants and like contaminants in the exhausts of pneumatic devicesmay create working conditions that are unpleasant to many and a definitehealth hazard to some. operators. The mixture of moisture and lubricantin the exhausts to ambient atmosphere in a plant leave a noticeablerancid or fetid odor-which is objectionable to many operators; even inplants which are well-ventilated and air-conditioned, pneumatic toolscan create a noticeable haze in the area of use. Some workers have ordevelop allergic responses to such contaminated air.

Aside from the threat to the health and comfort of operators, anotherproblem created by the contaminants in the exhausts of pneumatic devicesarises from the fact that efficient soundmufflers depend at least inpart upon diffusion of the exhaust through porous accoustical elements(which may vary from perforated metal and screens to loosely felted orpacked fibrous or granular material or poroussintered metal or ceramicmaterials or various combinations). The tortuous passages andinterstices of these porous elements become clogged, and oftenrelatively rapidly, with the entrained contaminants which may form gumsand gels in the passages. Such clogging of the'accoustical elements can'create back-pressures which interfere with the efficiency of thepneumatic devices, particularly valves,

brakes, and clutches whose effective operation may depend oninstantaneous exhaust of the operating air. In any given muffler therate of clogging and the consequent build-up of back-pressures beyondtolerable limits is relatively unpredictable; heretofore the only curefor the problem was a maintenance program requiring frequent changes ofthe mufflers or at least their accoustical elements regardless ofwhether a change was actually needed or not.

It is an object of this invention to provide an accoustical mufflerwhich is provided with means to classify and separate from the exhaustsof pneumatic devices the entrained moisture and lubricants in liquidform and to cause or allow the separate discharge of such liquid. Theeffective life of the accoustical element is thereby greatly prolongedand the hazard to health and pleasant working conditions is greatlyincreased. Other and further objects and advantages of this inventionwill be apparent from the following specification, claims and drawings,in which:

FIG. 1 is a top plan view of an embodiment of this invention. i

FIG. 2 is a vertical cross-section through the line 2-2 of FIG. 1.

FIG. 3 is'an enlarged fragmentary view, partly in section, of thecollector shown in FIG. 2.

5 Referring to the drawings, the muffler iscomprised ting ofa pneumaticdevice. Thecap 10 has a peripheral internal flange 12 providing a seatfor the body 20. The seat of the flange 12 is axially spaced from theboss 11 by the wall 14 to provide a dome-shaped expansion chamber 15,having a pair of small internal bosses l6 tapped to receive thetie-bolts 17.

The body 20 comprises a cylindrical wall 21 constituting the porousaccoustical element of the muffler; in this instance, the wall 21 iscomprised of loosely felted cellulosic fibers bonded together to theextent necessary for mechanical strength by suitable resinous binders.To protect the relatively soft and highly porous wall2l and providestrength for the axial compression load imposed by the tie-bolts 17, anouter covering of perforated metal or screen 22 is provided. Thethickness of the wall 21 should be sufficient so that, as the exhaustair escapes through the tortuous passages provided by the wall 21, itsenergy is dissipated and thus its noise is reduced to the noise level orless of the ambient noise at the site of the muffler. The length anddiameter of the silencing chamber 23 thus provided by the body 20depends upon the porosity of the wall material 21 and should provide anarea for escape of the exhaust air whereby the pressure differentialbetween the chamber 23 and the ambient atmosphere will create a'minimalback-pressure well belowthat tolerated by the equipment to which themuffler is connected.

the collector sufficient to create a consequent pressure differentialbetween the exhaust air as it enters the domed expansion chamber and asit enters the chamber 23 from the end 26; in the preferred constructionshown, the cross-sectional area of the opening 26 the shell 24, theopening 26 is defined by an inwardly extending flange 27 provided on itsinner edge 'with drop-forming dimples 28. To allow the tie-bolts 17 topass through the collector 24, it and its flange 25 are drilled orprovided with slots 29 on opposite sides of the collector.

The silencing chamber 23 may be closed by a base 30 which is preferablyan inverted substantial duplicate of the cap 10. That is, it is providedwith a central internally threaded boss 31 and a circumferentialinternal flange 32 providing a seat for the body 20, the flange 32 andboss 31 being axially spaced and connected by a wall 34 to provide asump 35. The base is preferably completed by a baffle plate 37 heldbetween seats of the flange 32 and the lower end of the body to partlyclose off the lower end of the silencing chamber 23. in this particularembodiment, the baffle plate 37 is a disk of perforated metal, but maybe of screening or other porous material, such as sintered metal, whichwill allow liquid dropping from the collector 24 to pass into the sump35 but impede the turbulence of the air escaping through the opening 26of the collector to minimize any re-entrainment of the liquid by suchair so as to carry it to the porous wall 21. The base 30 is providedwith a pair of small internal bosses 36 similar to the bosses 16 butdrilled to receive the tie-bolts 17 by which the muffler cap 10, body20, and base 30 may be assembled and disassembled to allow eventualreplacement of the wall 21 of accoustical material.

Various means for the necessary draining of the sump 35 may be employed,depending upon the maintenance requirements and program of the user. Ifthe general working conditions are such that optimum noise reduction isnot required and slow but a relatively continuous drip from'the mufflercan be tolerated, the simplest expedient is to simply leave the boss 31open so that the separated liquid can drop to a receptacle as it flowsfrom the sump; as discovered in connection with the Fail-safe Mufflerdisclosed in my copending application, Ser. No. l75.l7 5, filed Aug. 26,1971, (now US. Pat. No. 3,688,868) it is not necessary for substantial,though less than optimum, noise reduction to completely close off thesilencing chamber rather, so long as the porous material of the wall 21is relatively unclogged. a baffle plate, such as the plate 37, and anopen base, such as the base 30, will produce such substantial noisereduction. 1f continuous dripping from the sump 35 can be tolerated butoptimum noise reduction is desired, the boss 31 may be closed by aconventional breather" plug having a center section of porous sinteredmetal through which the accumulated liquid can drain. The pores of thesintered metal in such a breather plug willeventually clog and need tobe replaced or cleaned, but only atrelatively infrequent intervals.

If optimum noisereduction is desired but continuous drainage of theodorous liquid from the muffler is undesirable, the automatic dischargemeans shown in FIG. 2 may be employed. That is, a length of accumulatortube or pipe 40 is threaded into the boss 31, the lower end of the tube40 being closed by a cap 41. The longer leg of an inverted U-shapedsiphon tube 42 extends through the cap 41, its shorter leg ending abovethe inside of the cap. Separated liquid from the sump 35 accumulates inthe tube 40 until its level rises to the upper end of the siphon. Aidedslightly by the small static pressure differential between the silencingchamber 23 and the ambient atmosphere, gravity then starts the flowthrough siphon 42 to quickly empty the liquid in the accumulator tube 40into a suitable receptacle or the like placed below it. The siphon tube42 and cap 41 shown in FIG. 2 may, of course, be omitted and replaced bya conventional pipe cap; in such case the accumulator tube will requireemptying at scheduled periods unless a small drain hole is drilledthrough the upper end of the accumulator so that dripping from itsignals the need for emptying the accumulator. If either alternative ofthe above described accumulator tube is employed, the baffle 37 becomesrelatively superfluous and may be omitted; the velocity of the portionof the air from the collector opening 27 which can enter the tube 38 isbaffled by the opening in the boss 31 and by the tube; any drops whichmay then fall directly to the floor of the sump 35 will tend to draininto the tube 38 rather than be re-entrained by air which is directed bythe sump to its escape through the wall 21.

Irrespective of the various available means which may be employed forthe necessary drainage of the sump 35, the key to the operation ofamuffler made according to the invention lies in the collector meansexemplified by the collector 24. Air enters the expansion dome 15 withsubstantial kinetic energy. As such air rapidly expands in the dome andits extension provided by the collector 24, the majority of it loses itsvelocity and capacity for entraining liquid droplets while striking theconverging internal surface of the collector, which surface isconfigured so as to have a substantial component perpendicular to theflow of the incident expanding air and to reflect such impinged airdownwardly toward the collector opening 26. Droplets of moisture andlubricant are either entrained in the exhaust as it enters the dome 15or are formed by the rapid cooling of the vapors in the exhaust as itexpands upon discharge from the line to which the boss 11 is connected;such droplets tend to adhere to the wall of the collector as the exhaustimpinges upon it. As shown in FIG. 3, these adhered droplets then draindown the steep internal surface of the collector 24, merging into largerdroplets as they approach and collect on the lower flange 27 of thecollector 24. The ring of liquid which then collects on the flange 27 isdrained in large drops by gravity and the flow of air through theopening 26; these drops being of sufficient mass to minimizereentrainment by the exhaust air as it re-expands into the silencingchamber 25. The dimples or ruffles 28 in the inner edge of the flange 27aid in the formation of such relatively massive drops which fall to thebaffle 37 or directly onto the floor of the sump 35.

The stripping of entrained moisture and lubricant from the exhaustentering the dome 15 is by no means totally complete, but thesubstantial amount separated greatly reduces the rate of clogging of theporous wall 21 and allows that wall to function longer as an effectivefurther filter of the exhaust dissipated through it.

This invention is not to be limited to the specific embodiment disclosedin the drawings and its modifications as described but may be furthermodified by those skilled in the art without departing from the scopedefined in the appended claims.

What is Claimed is:

' l. A muffler for classifying and separating entrained liquid from apneumatic exhaust before dissipation of viding tortuous passages throughwhich said exhaust air may dissipate at a velocity substantially lessthan that at which the exhaust enters said muffler and the entrance ofsaid drain opening through said bottom member being located inwardly ofsaid wall, and a collector mounted withinsaid muffler to define anexpansion chamber which extends from said top member into said silencingchamber, said collector having an internal frusto-conical surfaceconverging toward a lower opening larger than the inlet in said topmember and spaced from said bottom member to permit a pressure drop fromsaid inlet to said lower collector opening and the expansion of airwithin said expansion chamber, said comprising sound-deadeningacoustical material procollector surface being positioned with respectto the direction of flow of a majority of said expanding air so as to beimpinged upon thereby at an angle having a substantial componentperpendicular to said surface to reflect such impinging air downwardlythrough the lower opening of said collector so that substantially allair leaving said expansion chamber is directed toward said bottommember, whereby droplets of liquiden trained in said air as it impingesupon said collector surface will collect thereon to then drain throughsaid lower collector opening and drop through said silenc ing chamber tosaid bottom member in substantially reentrainment-inhibiting drops.

2. A muffler as definedin claim 1 wherein said lower opening in saidcollector is defined by an'inwar'dly extending flange upon which saiddroplets may collect I prior to dropping through said silencing chamberto said bottom member.

3. A muffler as defined in claim 2 in which said collector has aninternal frusto-conical surface converging toward said lower opening,said' surface being positioned with respect to the direction of flow ofa major- 6 ity of said expanding air so as to be impinged upon therebyat an angle having a substantial component perpendicular to said surfaceand to reflect such impinging air downwardly toward said lower opening.

4. A muffler as defined in claim 2 in which the inner edge of saidflange on said lower opening is provided with irregularities to aid inthe formation of drops of liquid flowing'from the flange which are ofsufficient mass to allow such drops to fall through the air in saidsilencing chamber to said bottom member without substantialre-entrainrnent as said air re-expands from said lower opening into saidsilencing chamber.

5. A muffler as defined in claim 2 in which said bottom member isdepressed below said porous wall to provide a sump for receiving dropsfrom the lower opening of said collector for flow to the drain openingtherein.

6. A muffler as defined in claim 5 including baffle means over said sumpto permit liquid from said lower opening of said collector to drainthrough to said sump but to impede the flow of air into and out of saidsump.

7. A muffler as defined in claim. 6 includingporous means in the drainopening of said sump to allow liquid to drain therethroughbut closingthe interior of said silencing chamber from direct access to the ambientatmosphere.

8. A muffler as defined in claim 5 in which the drain opening of saidsump is connected to a removable re-, ceptacle for accumulating thedrainage of said sump and means therein for signalling the accumulationof sufficient drainage to require removal and emptying of saidaccumulator receptacle.

9. A muffler as defined in claim 5 in which the drain opening of saidsump is connected to a receptacle for accumulating drainage from saidsump and automatic means for emptying the accumulator receptacle ofdrainage therein. I

10. A muffler as defined in claim 9 in which said automatic meanscomprises an inverted U-shaped siphon tube having a longer downward legextending through the bottom of said accumulator receptacle and ashorter upward leg having an opening terminating within the receptacleabove the bottom thereof and the connection of the downward leg to theupward leg is at a height sufficient to provide a head above the openingin the shorter leg which is greater than the static pressuredifferential between the interior of the accumulator receptacle and theambient atmosphere whereby,

when said drainage accumulates in said receptacle to a levelcommencingto submerge said siphon tube, the accumulator receptacle isdrained by gravityto the level of the opening of said shorter leg.

1. A muffler for classifying and separating entrained liquid from apneumatic exhaust before dissipation of the exhaust to ambientatomosphere comprising a top member adapted to be connected to theexhaust outlet of a pneumatic device and provided with an inlet forintrodUcing exhaust air into said muffler, a bottom member having adrain opening through which separated liquid may be drained, avertically-extending porous wall between said top member and bottommember to define an internal silencing chamber, said wall comprisingsound-deadening acoustical material providing tortuous passages throughwhich said exhaust air may dissipate at a velocity substantially lessthan that at which the exhaust enters said muffler and the entrance ofsaid drain opening through said bottom member being located inwardly ofsaid wall, and a collector mounted within said muffler to define anexpansion chamber which extends from said top member into said silencingchamber, said collector having an internal frusto-conical surfaceconverging toward a lower opening larger than the inlet in said topmember and spaced from said bottom member to permit a pressure drop fromsaid inlet to said lower collector opening and the expansion of airwithin said expansion chamber, said collector surface being positionedwith respect to the direction of flow of a majority of said expandingair so as to be impinged upon thereby at an angle having a substantialcomponent perpendicular to said surface to reflect such impinging airdownwardly through the lower opening of said collector so thatsubstantially all air leaving said expansion chamber is directed towardsaid bottom member, whereby droplets of liquid entrained in said air asit impinges upon said collector surface will collect thereon to thendrain through said lower collector opening and drop through saidsilencing chamber to said bottom member in substantiallyreentrainment-inhibiting drops.
 2. A muffler as defined in claim 1wherein said lower opening in said collector is defined by an inwardlyextending flange upon which said droplets may collect prior to droppingthrough said silencing chamber to said bottom member.
 3. A muffler asdefined in claim 2 in which said collector has an internalfrusto-conical surface converging toward said lower opening, saidsurface being positioned with respect to the direction of flow of amajority of said expanding air so as to be impinged upon thereby at anangle having a substantial component perpendicular to said surface andto reflect such impinging air downwardly toward said lower opening.
 4. Amuffler as defined in claim 2 in which the inner edge of said flange onsaid lower opening is provided with irregularities to aid in theformation of drops of liquid flowing from the flange which are ofsufficient mass to allow such drops to fall through the air in saidsilencing chamber to said bottom member without substantialre-entrainment as said air re-expands from said lower opening into saidsilencing chamber.
 5. A muffler as defined in claim 2 in which saidbottom member is depressed below said porous wall to provide a sump forreceiving drops from the lower opening of said collector for flow to thedrain opening therein.
 6. A muffler as defined in claim 5 includingbaffle means over said sump to permit liquid from said lower opening ofsaid collector to drain through to said sump but to impede the flow ofair into and out of said sump.
 7. A muffler as defined in claim 6including porous means in the drain opening of said sump to allow liquidto drain therethrough but closing the interior of said silencing chamberfrom direct access to the ambient atmosphere.
 8. A muffler as defined inclaim 5 in which the drain opening of said sump is connected to aremovable receptacle for accumulating the drainage of said sump andmeans therein for signalling the accumulation of sufficient drainage torequire removal and emptying of said accumulator receptacle.
 9. Amuffler as defined in claim 5 in which the drain opening of said sump isconnected to a receptacle for accumulating drainage from said sump andautomatic means for emptying the accumulator receptacle of drainagetherein.
 10. A muffler as defined in claim 9 in which said automaticmeans comprises an Inverted U-shaped siphon tube having a longerdownward leg extending through the bottom of said accumulator receptacleand a shorter upward leg having an opening terminating within thereceptacle above the bottom thereof and the connection of the downwardleg to the upward leg is at a height sufficient to provide a head abovethe opening in the shorter leg which is greater than the static pressuredifferential between the interior of the accumulator receptacle and theambient atmosphere whereby, when said drainage accumulates in saidreceptacle to a level commencing to submerge said siphon tube, theaccumulator receptacle is drained by gravity to the level of the openingof said shorter leg.